Electrohydraulic control means for machines employing plural hydraulic motors



June 26, 1951 J. B. CASTLE, JR. E AL 2,558,071

ELECTROHYDRAULIC CONTROL MEANS FOR MACHINES EMPLOYING PLURAL HYDRAULIC MOTORS 4 Sheets-Sheet 1 Filed lay s, 1946 INVENTORS 8. CA STL E JR.

JAMES AR THUR A SINCLAIR ATTORNEY June 26, 1951 J B. CASTLE, JR., E,T'AL 2,558,071

ELECTROHYD RAULIC CONTROL MEANS FOR MACHINES EMPLOYING PLURAL HYDRAULIC MOTORS Filed llay 3, 1946 4 Sheet-Sheet 2 l/JIIIII/ III/j 1/ o 53 nan-rum! wuvt I a J/ lan Bil is l TEAM TI Ill [fill Ill": Tr

U man I "I" L] mum R INVENTORS JAMES B. CASTL E ii? E A.

AT TORNEV v June 26, 1951 J. B. CASTLE, JR.. ET AL 1 2,558,071

mscmomnmuuc CONTROL MEANS FOR MACHINES v EHPLOYING PLURAL HYDRAULIC MOTORS Filed lay 3, 1945 4-Sheets-Sheet 3 I'I'l' I I INVENTORS' JAMES B. c.4511: JR. ARTHUR A. suvcum June 1951 J B. CASTLE JR. El AL 2,553,071

ELECTROHYfiRAULIC CONTRdL MEANS FOR MACHINES v EMPLOYING-PLURAL HYDRAULIC MOTORS Filed lay a, 1946 v I 4 Sheets-Sheet 4 lay 1:7

INVENTOR; JAMES B. CASTLE R. AYR THU '44. SINCLAIR A 7 TOPNEY Patented June 26, 1951 MACHINES EMPLOYIN LIC. MOTORS G PLURAL HYDRAU- James B. Castle, Jr., Oakland, and Arthur A. Sinclair, San Leandro, assignments, to said Earl W. Johnson,

Calif., assignors, by mesne James B. Castle, Jr., and both of Oakland, Calif.

Application May 3, 1946, Serial No. 667,222

16 Claims.

Our invention relates to presses, and more particularly to a press brake and apparatus for controlling the movable blade thereof.

Among the objects of our invention are:

(1) To provide a novel and improved press brake or the like;

(2) To provide a novel and improved press brake or the like, wherein equalized movement of the movable blade is assured in the operation of the machine;

(3) To provide -in connection with a press brake or the like, novel and improved means for leveling the blade of such machine;

(4) To provide a novel and improved press brake or the like, wherein the stresses developed of the machine.

In general, the invention relates to a press brake or the like wherein a pair of cooperating blades of substantial width are brought together to perform an operation, and the invention contemplates not only the incorporation of a system therein which will assure equalized movement of the movable blade of the machine, but also a machine which will withstand excessive stresses with a minimum of built-in weight.

Referring to the drawing for detail, the specific embodiment 'of our invention as illustrated therein in the form of a press brake, comprises a pair of side plates l and 3 formed to provide work-clearance notches 5 in the front edge thereof, the Side plates being connected across their front edges below the work-clearance notches, by a lower front stationary blade 1 which is preferably formed with a depending apron 9 adapted for anchoring in the concrete foundation l I usually provided for the installation of a machine of this type.

An upper front movable blade I3 is slidably mounted in guides on the front edges of the side plates above the work-clearance notches. The opposing edges or the blades are designed ill 2 to carry complementary components of a forming die (not shown) Pivotally disposed at the rear of each side plate is an hydraulic cylinder l5 enclosing a piston I! having a piston rod l9 extending upwardly therefrom. At an intermediate point on each side plate between the upper front blade and the hydraulic cylinder, there is pivotally mounted a link 2| adapted to act as a movable fulcrum for a lever 23 having one end pivotally connected to the upper edge of the movable blade and its other end pivotally connected to the piston rod of the associated hydraulic cylinder. Preferably, the fulcrum on each side plate' is disposed closer to the movable blade than to the associated hydraulic cylinder to obtain a mechanical advantage whereby the hydraulic cylinder may be of relatively small size, yet capable of transmitting powerful forces to the movable blade in its downward movement toward the lower fixed blade, to accomplish a machine operation.

During this operating stroke of the machine, the stresses developed at the fulcrum mounting are upward. Being applied as they are however, at a location in approximate line with the interior edge of the work clearance notch, a relative light weight side plate can adequately absorb such stresses without buckling or distortion.

Importance must be attached to the pivotal mountings and connections previously indicated, for it is only by reason of these that the arrangement and advantages described are possible.

Each cylinder is part of an independent hydraulic system which, in addition to the hydraulic cylinder l5, includes a pump 25, a tank or reservoir 21, a pair of lines 29 and 3| leading each to one end of the cylinder, and a reversing valve 33 installed in the lines and adapted to interchangeably connect the lines between the discharge of the pump and the reservoir.

. Such reversing valve may be of the type schematically illustrated in conjunction with the circuits of Figure 3, and may comprise a valve body 35 having a'pair of diametrically disposed openings 31 and 39 for connection to the pump discharge and reservoir respectively, and a second pair of diametrically disposed openings ll and 43 for connection to the upper and lower ends respectively of a cylinder. An inner rotatable valve member 45 having oppositely disposed concave recesses 41 and 49 and a diametrical passage 5|, is aflixed axially to the midpoint of a lever 53 normally biased to a neutral position with'the passage Bl connecting the pump I of rotating the valve member in aclockwise direction through suflicient angle to bring the lines 29 and 3| into communication with the pump and reservoir respectively, while the other end of the lever is connected to the plunger of a solenoid 5'! capable when energized, of producing counter-clockwise rotation sufii'cient to bring the lines 29 and 31 into communication with the reservoir and pump respectively, or in other words to eflectively reverse the line connections.

The hydraulic system associated with one end of the upper or movable blade is designed to be as closely identical to the hydraulic system associated with the opposite end of the same blade,

' to realize like operating conditions and, as an aid toward this objective, the pumps are driven from r a single motor 59.

It is of prime importance in a press of this type that both ends of the movable blade should arrive at their destination at the same instant, for should one end arrive an instant prior to the other end, an imperfect operation will result.

In spite of the fact that both hydraulic systems are designed to be as closely identical as it is practical to realize, it has been universally found that in such a system one of the pistons will invariably tend-to lead or lag the other and, consequently, we have found it necessary to supplement the supposedly identical hydraulic systems with an equalizer system which will function in response to such unbalance to hold the pistons in line and thereby equalize the rates of movement of one end of the upper blade with respect tothe other end thereof.

Such equalizer system which we have illustrated specifically, is electrical in character and functions to adjust the piston pressures in a manner to compensate for unbalance, by bleeding some of the hydraulic fluid from one or the other of the hydraulic systems.

A bleeder passage Si in each hydraulic system is provided between the discharge of the pump and the reservoir, and such passage includes a normally closed bleeder valve 63 under control of an electrically energizable solenoid 65 associated therewith. Such solenoid is an element of an electrical circuit deriving energy from a common electrical power source 61 and controlled by the operation of a micro-switch 69 or ID as the case may be, of any conventional design and forming part of a switch assembly .H.

The particular type of micro-switch illustrated (Figure 5) includes a contact 13 and an armature l5 actuated through the application of a slight pressure to a push pin 11 constituting part of the switch structure.

Both micro-switches 69 and are carried on a link 19 to form a unit, which is floated between a spring 8| anchored at one end under tension, to the rear of the lower fixed blade I, and a Bowden wire 83 extending through a fixedly mounted guide tube 85 to a point adjacent the opposite end of the upper movable blade l3, at which point the Bowden wire is anchored.

Associated with the micro-switches and con stituting a component part of the switch assembly H, is a switch actuator means in the form of an actuating rod or finger 81 mounted on a similar but independent link 89 which is floated between a spring 91 anchored at one end under tension to the rear of the lower fixed blade, and a Bowden wire 93 passing around a directionreversing pulley 95 mounted on the rearof the lower fixed blade at the other end thereof, before passing through a fixedly mounted tube 91 at the opposite end of the machine to an anchoring point adjacent that end of the upper blade opposite that at which the first Bowden wire was afilxed.

The initial adjustment of the micro-switch assembly is such that the switch actuating rod or finger 81 lies in spaced relationship to the push pins ll of the micro-switches, thereby causing each micro-switch to be normally in open circuit condition.

As the upper blade 13 is lowered to perform a machine operation, both floating components of the micro-switch assembly will move in the direction of pull exerted by their respective tensioning springs. The movement of one of these floating components will, of course, be under control of one end of the movable blade while the other floating component of the assembly will be under control of the opposite end of the movable blade. Consequently, as long as both ends of the movable blade travel at the same instantaneous velocity or rate and maintain symmetry of movement, the relationship of the actuating rod or finger with respect to the microswitches will be maintained, and the microswitches will remain in open circuit condition. Under these conditions, the hydraulic systems are functioning properly and will not be disturbed.

On the other hand, any departure from the above relationship in the movement of the upper blade, will produce a relative movement between the floating components of the micro-switch assembly, with the result that one or the other of the armatures will be urged into circuit closing engagement with its associated contact. That hydraulic system which is responsible for the more rapid movement of the one end of the upper blade will have its bleeder valve opened and for such brief interval of time only as is necessary to reestablish the equalized movement of both ends of the blade in question, and this will of course be followed by an instantaneous reestablishment of the neutral position of the actuating rod and consequent deenergization of the pertinent electrical circuit. The corrective changes are for all practical purposes instantaneous, an accomplishment due in large measure to the sensitivity of the conventional type micro-switch used, and the rapid drop in hydraulic pressure permitted by the bleeding from the system of a very minute portion of the liquid. I

On the return stroke of the upper blade to its initial starting position, it is just as essential that equalized travel be maintained to assure proper starting conditions for the subsequent down stroke. Inasmuch as the corrective factors for the up stroke should be the reverse of those on the down stroke, a circuit reversing means 99 is installed in the circuit between the-microswitch assembly and the bleeder valve solenoids, and is made responsive to controlled operation of the machine.

Such controlled operation entails a foot controlled pedal ID! for initiating movement of the upper blade through application of power to electrically controlled circuits, and a microswitch gauge I03 for disconnecting such power at either end of a stroke, in addition to energizing a reversing circuit for both the hydraulic systems and the bleeder valve solenoid circuits.

The micro-switch gauge includes a bracket HIS mounted adjacent the front edge of one of the side plates I pr 3 and carrying an upper, microswitch III! of 'a normally'open type and a lower micro-switch I09 of a normally closed type.

- Mounted on the upper blade and at approximicro-switch, the arms and associated bolts being so disposed that the upper micro-switch will be actuated at the desired lower limit of the down stroke of the blade, while the lower switch will be actuated at the desired upper limit of the up stroke of the blade.

The foot control pedal actuates the armature I2I of a two-way switch I23, and is normally biased by a spring I25 to an up position. The foot switch armature is normally connected .to one side of the power source 61. and in the up position of the foot pedal, it effects a connection from that side of the power source throughthe winding of a relay I21 and the normally closed micro-switch I09 back to the other side of the power source, to thereby energize the aforementioned relay. This relay in its deenergized condition is of the normally open contact type and having but a single pair of circuit closing contacts I 29, and when energized, serves to close a circuit from one side of the power source through corresponding solenoids 55 which determine the flow of fluid from the pumps 25 to the upper ends of the respective cylinders I5,

- and thereby bring about the upstroke of the upper blade.

\ During the period of this upward stroke of the blade, during which interval of time the contacts I29 of the relay I21 remain closed, a, circuit is established from'the power source through the winding of a reversing relay I35 by 'way' of these contacts I29. This relay carries a pair of armatures I31 and I39, each adapted to efiect connection between one or another of a pair of contacts, depending on the condition Of the relay.

The reversing relay is associated with the micro-switch assembly II of the compensating circuit, and serves to cause energization of one or the other of a pair of like relays HI and I43, each of which has a single pair of contacts adapted to close the circuit through one of the bleeder valve solenoids 65.

The circuits involve a common connection I45 from one of the contacts of each of the microswitches 69 and III to one side of the power circuit, and a separate connection I41 or I49 respectively from the remaining contact of each micro-switch to one of the armatures I31 and I39 respectively of the reversing relay I35.

Corresponding contacts associated with each of the armatures are connected to diflferent ones of the similar relays HI and I43, and accordingly these relays will be energized to the exclusion of one another, depending upon which of the microswitches in the switch assembly h-appens'to be actuated.

Which of these relays HI and I43 becomes energized, will in turn determine which of the bleeder valve solenoids 65 becomes energized. The reversing relay I35, therefore, will interchange these relays I and I43 for the up and line with the push pin II! of the associated chine comes to rest, for the down-stroke sole-.

noids 51 can only be energized when the foot pedal IIII is depressed.

Therefore. to initiate a downward stroke of the blade, the operator will put pressure on the foot pedal to the extent of making contact between the foot lever and the upper contact of the foot switch, whereby to energize the downstroke solenoids 51 through normally closed contacts I5I of a relay I53 of a type similar to that of the reversing relay I35 previously described.

The winding of this relay is connected to the source of power through each of the microswitches I01 and I09, associated with the gauge I I03, but inasmuch as the upper micro-switch III] is of the normally open type, the relay will not be energized until this particular micro-switch is closed, which occurs at the lower extremity of the downstroke of the blade.

When this point is reached, however, the circuit through the winding of relay I53 is completed and the solenoid becomes energized and opens the circuits to the downstroke solenoids 51, and in so doing connects the upstroke solenoids in circuit across the power source, and starts the blade in reverse, which immediately re-opens micro-switch I01 and would normally break the circuits to the upstroke solenoids.

This is precluded, however, by the establishment of a holding circuit through the second armature I55 on the relay and such holding circuit will include thelower normally closed microswitch I09, and shunt out the now open microswitch I01. Such holding circuit will continue to energize the relay I53 until the normally closed micro-switch I09 is actuated to open condition at the extremity of the upward stroke of the blade. at which time the machine comes to a halt At such time as the-machine comes to a halt, neither the downstroke nor upstroke solenoids are energized and consequently the spring bias on the valves 33 are permitted to restore the valves to their neutral positions wherein the pumps are disconnected from the cylinders I5 and pump directly into the reservoir or tank or in other words, idle.

Thus it has been shown how the blade leveling system of the invention can function to maintain symmetry of movement of the blade from one end to the other, both on the upstroke as well as the downstroke, and how the necessary reversal of the leveling circuits is accomplished at the proper times through cooperation with the circuits for.controlling machine operation.

Therefore, while we have disclosed \our invention in its preferred form and in considerable detail, the same is subject to modification and alteration without departing from the underlying principles and we, accordingly, do not desire to be We claim:

1. In a machine wherein a pair of cooperating members of substantial width are brought togather to perform an operation of said machine, means for controlling the forward and reverse stroke of one of said members, said means including a separate hydraulic drive system for each end of said member and involving a cylinder and included piston in drive connection to said member, a reversing valve in each of said hydraulic systems for determining the forward or reverse direction of movement of said member, and a control system for determining the operating conditions of said valves; means for equalizing the movement of said member during both its forward and reverse strokes, said means being responsive to a departure from equalized movement of said member for bleeding one or the other of said hydraulic systems until equalized movement of said member is reestablished, and involving a normally closed solenoid-operated valve in shunt with each of said cylinders, an electrical energizing circuit for each of said valves including a switch, and means for selectively actuating one of said switches in accordance with the end of said element which advances ahead of the other; and means for reversing the association of said valves relative to said switches on reverse strokes of said member.

2. In a machine wherein a pair of cooperating members of substantial width are brought toward each other to perform an operation of said machine, one of said members having a piston at each end to drive the same; a hydraulic system for each of said pistons, each said hydraulic system comprising a pump, a cylinder enclosing one of said pistons, a fluid circuit between said pump and cylinder, a pump driving motor in drive connection to the pump of each hydraulic system; and means responsive to the relative advance of any one of said pistons during movement of said member, for effectively disconnecting operating pressure from the associated cylinder, said means including a low resistance passageway bypassing said cylinder, and a normally closed valve blocking said passageway and adapted for instantaneous opening upon occurrence of the relative advance of such piston.

3. In a machine wherein a pair of cooperating members of substantial width are brought toward each, other to perform an operation of said machine, a piston at each end of one of said members and operatively connected thereto to drive said member; a hydraulic system for each of said pistons, each said hydraulic system comprising a pump, a cylinder enclosing one of said pistons, a fluid circuit connecting the output of said pump to one end of said cylinder and the other end of said cylinder to the input of said pump, and means responsive to a slight relative advance of any one of said pistons during movement of said member for substantially instantaneously removing the hydraulic pressure from said piston, said means including a low resistance passageway connecting the output of said pump tothe input thereof, a normally closed solenoid-controlled valve in said passageway adapted, when energized, to unblock said passageway and permit the same to carry the discharge from said pump, a plurality of microswitches corresponding in number to the number of such pistons, each of said micro-switches being connected in circuit with one of said solenoidcontrolled valves.

4. In a machine wherein a pair of cooperating members of substantial width are brought toward each other to perform an operation of said machine, a piston at each end of one of said members and operatively connected thereto to drive said member; a hydraulic system for each of said pistons, each said hydraulic system comprising a pump, a cylinder enclosing one of said pistons, a fluid circuit connecting the output of said pump to one end of said cylinder and the other end of said cylinder to the input of said pump; and means responsive to a slight relative advance of any one of said pistons during movement of said member for substantially instantaneously removing the hydraulic pressure from said piston, said means including a low resistance passageway connecting the output of said pump to the input thereof, a normally closed solenoidcontrolled valve in said passageway adapted, when energized, to unblock said passageway and permit the same to carry the discharge from said pump, a plurality of normally open micro-switches corresponding in number to the number of such pistons, each of said micro-switches being connected in circuit with one of said solenoid-controlled valves, and means for selectively closing that micro-switch whose associated solenoidcontrolled valve is in the hydraulic system of the advanced piston.

5. In a machine wherein a pair of cooperating members of substantial width are brought toward each other to perform an operation of said machine; means for establishing a forward and return stroke of one of said members, said means including a separate hydraulic drive system for each end of said member and involving pump means, a cylinder having a piston there in operatively connected to said member, a reservoir, and a hydraulic line from said pump means to said cylinder and a hydraulic line from said cylinder to said reservoir and from said reservoir to said pump means; and means for equalizing the movement of both ends of said member during its forward movement toward said other member, said means including a normally closed valve in each of said hydraulic systems in by-pass relationship to the cylinder therein, and means responsive to a relative advance between one end of said member and the opposite end thereof for opening the valve associated with the advanced end of said member.

6. In a machine wherein a pair of cooperating members of substantial width are brought toward each other to perform an operation of said ma-.

chine; means for establishing a forward and return stroke of one of said members, said means including a separate hydraulic drive system for each end of said member and involving pump means, a cylinder having a piston therein connected to said member, a reservoir, a hydraulic line from said pump means to said cylinder and a hydraulic return line from said cylinder to said reservoir, control means involving circuit make-and-break means responsive to forward movement of said member at its desired forward limit of travel for reversing said hydraulic line connections to said cylinder; means for equalizing the movement of both ends of said member during its forward movement toward said other member; and means upon the completion of such forward movement as determined by said control means, for reversing said movement equalizing means to render said movement equalizing means also effective on the return movement of said member.

7. In a machine wherein a pair of cooperating members of substantial width are brought to-' 9 ward each other to perform an operation of said machine; means for establishing a forward and return stroke of one of said members, said means including a separate hydraulic drive-system for each end of said member and involving pump means, a cylinder having a piston therein operatively connected to said member, a reservoir, and a hydraulic .line from said pump means to said cylinder and a hydraulic line from said cylinder to said reservoir and from said reservoir to said pump means; means for equalizing the movement of both ends of said member during its forward movement toward said other member, said means including a normally closed valve in each of said hydraulic systems in by-pass relationship to the cylinder therein, means responsive to a relative advance of one end of said member relativeto the other for opening the valve associated with that end of said member; and means for reversing the association of said valves and said advance responsive means during the return movement of said member to render said movement equalizing means also eifective on such return movement.

8. In amachine wherein a pair of cooperating members of substantial width are brought toward each other to perform an operation of said machine, and a piston is located at each end of one of said members; a hydraulic system for each of said pistons, each said hydraulic system comprising a pump, a cylinder enclosing one of said pistons, a fluid line connecting the output of said pump to one end of said cylinder and the other end of said cylinder to the input of said pump, and valve means for reversing the fluid line connections between said pump and cylinder to determine the forward and return movements of said member, said valve means including means for determining a static condition of said member; and means for controlling the operating positions of said reversing valve means to determine the start and finish points in the stroke of such member with respect to the other member of said pair, said means involving a bracket mounted on a stationary portion of said machine, a pair of switches mounted in vertically spaced relationship on said bracket, an electrical control circuit interconnecting said reversing valve means and said switches, and switch actuation means mounted on said controlled member for movement therewith in .a path occupied by saidv switches, said switch actuator means including an actuator element above the upper of said switches and an actuator element below the lower of said switches.

9. In a machine wherein a pair of cooperating members of substantial width are brought toward each other to perform an operation of said machine, and a piston is located at each end of one ofsaid members to drive the same; a, hydraulic systemfor each of said pistons, each said hydraulic system comprising a pump, a cylinder enclosing one of said pistons, a fluid line connecting the output of said pump to one end of said cylinder and the other end of said cylinder to the input of said pump, and valve means for reversing the fluid line connections between said pump and cylinder to determine the forward and return movements of said member, said valve means including means for determining a static condition of said member; and means for controlling the operating positions of said reversing valve means to determine the start and finish points in the stroke of such member with respect to the other member of said pair, said means involving a bracket mounted on a sta tionary portion of said machine, a pair of microswitches mounted in vertically spaced relatiom ship on said bracket, an-electrical control circuit interconnecting said reversing valve means and said switches, and switch actuation means mounted on said controlled member for movement therewith in a path occupied by said microswitches, said switch actuator means including an actuator element above the upper ofsaid micro-switches and an actuator element below the lower of said micro-switches and means for adjusting the spacing between each of said actuator elements and its associated switch.

10. In a machine wherein a pair of cooperating members of substantial width are brought toward each other to perform an operation of said machine, and a piston is located at each end of one of said members to drive the same; a hydraulic system for each of said pistons, each said hydraulic system comprising a pump, a cylinder enclosing one of said pistons, a fluid line connecting the output of said pump to one end of said cylinder and the other end of said cylinder to the input of said pump, and valve means for reversing the fluid line connections between said pump and cylinder to determine the forward and return movements of said member, said valve means including means for determining a static condition of said member; means for controlling the operating positions of said reversing valve means to determine the start and finish points in the stroke of such member with respect to the other member of said pair, said meansinvolving a bracket mounted on a stationary portion of said machine, a pair of micro-switches mounted in vertically spaced relationship on said bracket, an electrical control circuit interconnecting said reversing valve means and saidswitches, and switch actuation means mounted on said controlled member fdr movement therewith in a path occupied by said micro-switches, said switch actuator means including an actuator element above the upper of said micro-switches and an actuator element below the lower of said microswitches and means for adjusting the spacing between each of said actuator elements and its associated switch; and means for equalizing the movement of both ends of said controlled member during its movement toward said other member, said means including a normally closed solenoid controlled valve in each of said hydraulic systems in by-pass relationship to the cylinder in such system, and means responsive to a relative advance between one end of said controlled member and the opposite end thereof for opening the valve associated with said advanced end.

11. In a machine wherein a pair of cooperating members of substantial width are broughttoward each other to perform an operation of said machine, and a piston is located at each end of one of said members to drive the same; a

hydraulic system for each of said pistons, each reversing valve means to determine the start and finish points in the stroke of such member with respect to the other m mber of said pair, said means involvinga bracket mounted on a stationary portion of said machine, a pair of microswitches mounted in vertically spaced relationship on said bracket, an electrical control circuit interconnecting said reversing valve means and said switches, and switch actuation means mounted on said controlled member for movement therewith in a path occupied by said microswitches, said switch actuator means including an actuator element above the upper of said micro-switches and an actuator element below the lower of said micro-switches and means for adjusting the spacing between each of said actuator elements and its associated switch; means for equalizing the movement of both ends of said controlled member during its movement toward said other member, said means including a normally clomd solenoid controlled valve in each of said hydraulic systems in by-pass relationship to the cylinder in such system, means responsive to a relative advance between one end of said controlled member and the opposite end thereof for opening the valve associated with said advanced end; and means for reversing the association of said solenoid controlled valves and said advance responsive means during the return movement of said controlled member to render said movement equalizing means also effective on such return movement.

12. In a machine wherein a pair of cooperating members of substantial width are brought together to perform an operation of said machine, a system for assuring equalized approach of both ends of one of said members toward the other member, said system including a switch assembly comprising a pair of micro-switches mounted for movement as a unit and means associated therewith and responsive to movement relative to said micro-switches for establishing an electrical circuit through one of said switches in accordance with such relative direction of movement, means for moving said circuit-establishing means in accordance with movement of one end of said afore-mentioned member, means for simultaneously moving said micro-switches as a unit in the same direction as said circuitestablishing means in accordance with corresponding movement of the other end of said aforementioned member, said circuit-establishing means and micro-switches being initially adjusted to normally maintain open circuit conditions only so long as both ends of said aforementioned member move at the same instantaneous rates, and means responsive to establishing of a circuit through one of said switches, occasioned by a relative change in instantaneous rates between the ends of said member, for adjusting the instantaneous rate of travel of one of the ends of said aforementioned member in a direction to reestablish the open circuit condition of such micro-switch. l

13. In a machine having a movable member of substantial length, means for assuring equalized movement of said member at both ends, said means comprising a switch, assembly including two relatively movable components, one of said components embodying a pair of spaced circuit-y.

closing elements, said other component constituting a circuit actuator, means supporting said first component for movement in accordance with movement of one end of said member, means supporting said circuit actuator for independent movement between said spaced circuit closing 12 elements in accordance with movement of the other end of said member, said circuit actuator being normally in spaced relationship'to each of said circuit-closing elements during equalized travel of said member but adapted to actuate one or the other of said circuit-closing elements in response to unequalized movement of said member, and means responsive to the closing of one or the other of said circuit-closing devices for reestablishing equalized movement of said member.

14. In a machine wherein a pair of cooperating members of substantial width are brought toward each other to perform an operation of said machine, a hydraulic system for driving at each end of one of said members, each such hydraulic system comprising a pump, a cylinder having a piston in drive connection to an end of said membet, a fluid line connection from the output of said pump to one end of said cylinder and the other end of said cylinder to the input of said pump, means for interchanging fluid line connections between said pump and said cylinder to determine the forward and return movement of such member, means adapted to interconnect the output of said pump to its input for rendering ineffective such aforesaid fluid line connections between pump and cylinder and together with the other corresponding hydraulic circuit means, establishing a static condition of said member, means for equalizing the movement of the ends of said member during its forward movement, means actuable by an operator during a static condition of said member for establishing flow of fluid to an end of each cylinder to initiate a forward movement of said member, means responsive to movement of such member at its desired forward limit of travel for reversing the prevailing fluid line connections between pump and cylinder in each of said hydraulic circuits to automatically halt said forward movement and initiate a return movement of said member,

and means responsive to the return movement of said member at its desired limit of travel in such return direction, for controlling said interconnecting means to create a fluid connection between the output and input of the pump in each hydraulic system to establish a static condition of said member in the absence of actuation of said operator actuable means.

15. In a machine wherein a pair of cooperating members of substantial width are brought toward each other to perform an operation of said machine, a hydraulic system for driving at each end of one of said members, each such hydraulic system comprising a pump, a cylinder having a piston in drive connection to an-end of said member,,a fluid line connection from the output of said pump to one end of said cylinder and the other'end of said cylinder to the input of said pump, means for interchanging fluid line connections between said pump and said cylinder to determine the forward and return movement of such member, means adapted to interconnect the output of said pump to its input for rendering ineffective such aforesaid fluid line connections between pump and cylinder and together with the other corresponding hydraulic circuit means, establishing a static condition of said member, means for equalizing the movement of both ends of said member during its forward movement, means actuable by an operator during a static condition of said member for establishing flow of fluid to an end of each cylinder to initiate a forward movement of said member, means responsive to movement of such member at its desired forward limit of travel for reversing the prevailing fluid line connections between pump and cylinder in each of said hydraulic circuits .to automatically halt said forward movement and initiate a return movement of said member, means responsive to the return movement of said member at its desired limit of travel in such return direction, for controlling said interconnecting means to create a fluid connection between the output and input of the pump in each hydraulic system to establish a static condition of said member in the absence of actuation of said operator actuable means, and means for adjusting the point of response of said forward movement responsive means to shift the forward limit of travel of said member.

16. In a machine wherein a pair of cooperating members of substantial width are brought toward each other to perform an operation of said machine, a hydraulic system for driving at each end of one of said members, each such hydraulic system comprising a pump, a cylinder having a piston in drive connection to an end of said member, a fluid line connection from the output of said pump to one end of said cylinder and the other end of said cylinder to the input of said' pump, means for interchanging fluid line connections between said pump and said cylinder to determine the forward and return movement of such member, means adapted to interconnect the output of said pump to its input for rendering ineffective such aforesaid fluid line connections between pump and cylinder and together with the other corresponding hydraulic circuit means, establishing a static condition of said member,

'means for equalizing the movement of the ends of said member during its forward movement, means actuable by an operator during a static condition of said member for establishing flow of fluid to an end of each cylinder to initiate a forward movement of said member, means responsive to movement of such member at its deprevailing fluid line connections between pump and cylinder in each of said hydraulic circuits to automatically halt said forward movement and initiate a return movement of said member, means responsive to the return movement of said member at its desired limit of travel in such return direction, for controlling said interconnecting means to create a fluid connection between the output and input of the pump in each hydraulic system to establish a static condition of said member in the absence of actuation of said operator actuable means, means for adjusting the point of response of said forward movement responsive means to shift the forward limit of travel of said member, and means for adjusting the point of response of said return movement responsive means to determine the starting position of said member with respect to the work to be operated on.

JAMES B. CASTLE, JR- ARTHUR A. SINCLAIR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,925,236 Doyle et a1 Sept. 5, 1933 1,999,834 Ernst Apr. 30, 1935 2,148,543 Dinzl Feb. 28, 1939 2,169,113 Sheppard Aug. 8, 1939 2,312,213 Ferris Feb. 23, 1943 2,342,311 Thompson Feb. 22, 1944 2,343,167 Bench Feb. 29, 1944 2,353,388 Cannon July 11, 1944 2,353,389 Cannon July 11, 1944 2,359,961 Anthony Oct. 10, 1944 2,378,497 Phillips June 19, 1945 2,400,685 Collins May 21, 1946 2,410,603 Dubosclard Nov. 5, 1946 2,487,402 Watson Nov. 8, 1949 

